bz 1402867: Prevent scale down in scaling UI
bz 1402867: Prevent scale down in scaling UI

https://bugzilla.redhat.com/show_bug.cgi?id=1402867

In the scaling UI, added checks to allow scaling up but not down.
Scale down is handled explicitly via a separate UI action with
validation around maintenance mode on the node and lack of active
VMs.

ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic,ManageIQ/manageiq-ui-classic